414 GRAMINE^. 



15. Stipa. Glomes 2, membranaceous, awnless, nearly equal. PalcE coriaceous, involute : awn twisted. Scales shorter 



than the stipitate ovary. 



16. Abistida. Glumes unequal, mostly awnless. Faleee involute ; the lower with a 3-parted awn at the tip. 



Tribe 5. AGROSTIDE.E. Spikelcts one-flowered, rarely with another rudimentary flower. Glumes and palea 

 2, membranaceo-herbaceous ; the lower palea often awned. 



17. MuHLENBEH Gi A. Glumcs Unequal. Pales lanceolate, mostly hairy at the base ; the lower one mucronate or awned 



at the tip. — Panicle more or less contracted. 



18. ViLFA. Glumes unequal, not keeled. Pales not bearded ; the lower one awnless. 



19. Agrostis. Glumes unequal. Palese mostly shorter than the glumes : lower one commonly awned on the back ; 



the upper one often minute. — Panicle diffuse- 



20. Brachyelytrum. Glumes very minute. Lower palea with a long terminal awn ; upper with a clavate rudimen- 



tary flower at the base. — Panicle racemose. 



Tribe 6. ARUNDINACE.S!. Spikelets one-flowered, with a rudimentary flower; or many-flowered : the flowers 

 usually with long hairs at the base. Glumes and palese 2, membranaceo-herbaceous. — Inflorescence 

 paniculate. 



21. Calamagrostis. Spikelets one-flowered, and sometimes furnished with a pencil-form rudiment. Pales surrounded 



with hairs at the base j the lower one usually with a short awn at the apex or on the back. 



22. Ammophila. Pales shorter than the carinate glumes, surrounded with hairs at the base, awnless. Scales elongated. 



23. Phragmites, Spikelets 3 - 6-flowered : flowers perfect, on villous pedicels, except the lowest, which is sessile, 



staminate, and naked at the base. 



Tribe 7. CHLORIDE.^. Spikes unilateral : spikelets one-flowered, or many-flowered with the upper flowers 

 imperfect. Glumes and pales 2, herbaceo-membranaceous, 



24. Ei.Et7siNE, Spikes digitate or fasciculate. Spikelets sessile, 2 - 6-flowered : flowers awnless. Glumes carinate. 



Seed transversely rugose. 



25. Spartina. Spikes disposed in a raceme, or remote and secund. Spikelets unilateral, closely imbricated in 2 rows. 



Glumes and pales carinate, compressed, awnless. Styles mostly united below, 



26. BoXTTELOuA, Spikes short, disposed in a unilateral raceme. Spikelets 2 - 3-flowered. Glumes carinate ; the upper 



one much larger. Lower palea 3-toothed, or with 3 bristles at the summit. 



Tribe 8. AVENACE.S. Spikelets 2 - many-flowered ; the terminal flower usually imperfect Glumes and pales 

 2, herbaceo-membranaceous ; the lower palea usually with a twisted awn on the back, 



27. Aira. Spikelets 2 - 3-flowered. Lower palea 2 - 4-toothed, awned on the back. 



28. Trisetum. Spikelets 2 - 4-flowered. Lower palea bicuspidate, with a twisted awn on the back below the cusps. 



Caryopsis not sulcate. 



29. AvENA. Spikelets several-flowered ; the flowers remote. Lower palea awned on the back. Caryopsis longitudinally 



sulcate on the inside. 



30. Arrhenathertjm. Spikelets 2-flowered. Lower flower staminate, with the lower palea awned on the back. 



Upper flower perfect ; the lower palea awnless, or with a short awn a little below the tip. 

 31i Damthonia. Spikelets 2 - 5-flowered. Glumes longer than the flowers (which are bearded at the base), cuspidate. 

 Lower palea 2-toothcd, with a twisted awn between the teeth. 



32. UsALEPis. Spikelets 3 - 4-flowered, somewhat terete. Glumes short. Pales unequal, villous on the margins : lower 



one tricnspidate, the central cusp produced into a short awn ; the upper bicarinate and incurved. 



Tribe 9. PESTUCACEjE. Spikelets many-flowered (rarely few-flowered). Glumes and pales 2, membranaceo- 

 herbaceous, rarely coriaceous : lower palea often with a short bristle. Inflorescence paniculate, some- 

 times contracted and spike-like. 



33. PoA. Spikelets ovate, oblong or linear, compressed, 3 - many-flowered. Glumes shorter than the flowers. Paleae 



awnless, usually membranaceous, often with a web-like pubescence at the base. 



34. Glyceria. Spikelets terete, elongated, many-flowered. Palete awnless : upper one somewhat conduplicate. Scales 



collateral, connate. Stigmas decompound. 



35. Dactylis. Spikelets aggregated into a unilateral head, many-flowered. Glumes and palese carinate, mucronate. 



